1. Field of the Invention
The present invention refers to a disc brake for a vehicle wheel, the brake comprising a brake disc and brake shoes adapted to be brought into frictional engagement with the brake disc. The friction developed in such a brake between brake disc and brake shoes varies with the braking pressure applied and results in gradually reducing the rotational speed of the wheel and bringing the vehicle to a stop.
2. Description of the Prior Art
Brakes are standard equipment for motor-powered vehicles and are of prime importance for safe driving. Vehicles of former years were equipped with drum-type brakes, modern vehicles, on the other hand, are equipped with disc brakes, particularly if the braking power requirements are significant. Disc brakes can help generate higher braking power levels than drum-type brakes, because the parts rubbing against each other in disc brakes or, more specifically, the brake discs themselves are air-cooled. However, disc brakes possess the significant disadvantage of contributing to contaminating the environment. As a matter of fact, metal particles are rubbed off or abraded in the main from the brake shoes, but to some extent from the brake disc, and are blown off by the cooling air into the atmosphere, thus adding to environmental contamination. Considering the fact, that 4 to 8 brake shoes are used up per year and per vehicle, and that Switzerland has three million vehicles in use, one comes up with more than 819 metric tons of abraded metallic material per year for Switzerland alone. In addition there is a corresponding quantity of abraded adhesive material, which together with the stated abraded metallic material ends up getting in one way or another into cultured ground. The corresponding figures in the Federal Republic of Germany are 8500 metric tons of abraded dust, in Europe about 38,000 and in the whole world about 120,000 metric tons. Evidently, part of this abraded dust will first stay in the air for a shorter or longer time duration, and act as a toxic agent for the respiratory tract of both man and animal.